1. Field of the Invention
The present invention generally relates to image forming apparatuses such as a copier, a printer, a facsimile machine and a method for starting-up such apparatuses. More specifically, the present invention relates to image forming apparatuses and a method for shortening the time required for the starting-up of such an apparatus, after a main switch of the apparatus is turned on.
2. Description of the Related Art
In an image forming apparatus such as a copier, a printer or the like, image forming operations are performed after a main switch of the apparatus is turned on by a user. The temperature of a fixing unit subsequently reaches a set temperature after waiting for an amount of time therebetween, (i.e. starting-up time). The starting-up time may reach more than 5 minutes. Therefore, the starting-up time of the apparatus is not convenient for users operating such an apparatus.
During this starting-up waiting time, preparation of units other than the fixing unit, for example, image forming units such as a developing unit, a photosensitive body, a charging unit, a transferring unit, a photosensitive body, a charging unit, a transferring unit, a main control unit, and so forth is performed for image formation. Other operations which may be performed during the starting-up waiting time may include confirmation of toner temperature, checking of a remaining amount of toner, preliminary rotation of the transferring unit and photosensitive body, initialization and abnormality checking of each unit by the main control unit, and so forth. However, the preparation of the other units is completed within a short time period in comparison to that of the fixing unit. In general, a preparation time of a fixing unit (i.e. a time required for the temperature of the fixing unit to reach a temperature, at which a fixing operation can be performed properly, from a normal temperature or room temperature) is in the range of 1 to 5 minutes. In a remarkably fast case, this time is in the range of 15 to 20 seconds. In contrast to this, the preparation time of units other than the fixing unit is completed within a time range of approximately 5 to 30 seconds.
In order to shorten the starting-up time, various proposals have been made. For example, the starting-up time may be shortened as a result of maintaining an input current to an image forming apparatus at not more than a predetermined value, and controlling a current flowing into a fixing unit. Alternatively, an upper limit of a power level consumed by a fixing unit may be controlled to vary between a starting-up occasion of an apparatus and an ordinary occasion thereof to shorten the starting-up time. Specifically, preparation instructions are given to the fixing unit and the image forming units other than the fixing unit from a body control unit at an apparatus starting up time, and the upper limit of the power supplied to the fixing unit is set to a large value only at the starting-up occasion.
According to the above-described procedures for shortening the starting-up time, the purpose can be achieved to some degree. However, the limit of an input current to an image forming apparatus prevents the starting-up time from being further shortened.
Further, at a starting up time, a power level is provided to the body control unit, and preparation of image forming units other than the fixing unit is performed at the same time as preparation of the fixing unit. Therefore, it is required to maintain power at the level in which the preparation of the image forming units other than the fixing unit is completed, even though the preparation of the image forming units other than the fixing unit is completed. Thus, power is uselessly consumed until preparation of the fixing unit is completed.
Further, in the related art, in order to shorten the starting-up time of a fixing unit, preparatory heating is conducted such that power is supplied to a fixing heater even during a standby condition. Thereby, it is possible to perform image formation without requiring any waiting time. However, when the frequency of times of image formation is low, power is needlessly consumed for the preparatory heating.
An object of the present invention is to solve the above-mentioned problems occurring in the prior art, and to provide an image forming apparatus in which a fixing unit is started up rapidly.
Further, another object of the present invention is to provide an image forming apparatus which can be started up rapidly and consumes less power during a standby condition.
An image forming apparatus according to the present invention comprises:
a power supply switch for an apparatus body;
a first power supply unit to which AC power is supplied as a result of the power supply switch being turned on;
a second power supply unit to which AC power is supplied;
a first control unit which is supplied power through the first power supply unit and performs control such that the apparatus operates in a power saving mode;
a canceling device for generating a power-saving-mode-canceling signal to be input the first control unit;
a second control unit which is supplied power through the second power supply unit and performs control such that power is supplied to an image forming arrangement provided for performing an image forming process and the image forming arrangement is started up, when a predetermined condition is satisfied after the power-saving-canceling signal is generated;
a fixing unit which is supplied AC power through a switch device, has a fixing roller and fixes a toner image, formed on a recording sheet by the image forming arrangement using the fixing roller; and
a fixing-unit power changing arrangement for varying a level of power used by the fixing unit between a first predetermined fixing-unit power level and a second predetermined fixing-unit power level, the second predetermined fixing-unit power level being smaller than the first predetermined fixing-unit power level,
wherein:
the fixing unit is started up as a result of the switch device being turned on, which in turn is a result of the canceling device being turned on;
a power control signal for changing the level of power used by the fixing-unit power changing arrangement is generated within the fixing unit;
the fixing-unit power changing arrangement changes the level of power used by the fixing unit based on the power control signal so that, when the fixing unit is to be started up, the first predetermined fixing-unit power level is a level of power used by the fixing unit until a temperature of the fixing roller reaches a predetermined temperature, and the second predetermined fixing-unit power level is a level of power used by the fixing unit after the temperature of the fixing roller reaches a predetermined temperature, this condition being the predetermined condition.
Thereby, as a result of reducing a power level used by the arrangement other than the fixing unit and increasing a power level used by the fixing unit for heating the fixing roller at a time of starting up, it is possible to shorten the overall starting up time.
The fixing-unit power changing arrangement may change the level of power used by the fixing unit based on the power control signal generated inside the fixing unit or another power control signal generated by the first control unit.
When the power supply to the fixing unit is interrupted by some problem, such as a cover of the apparatus body being opened after the image forming apparatus moves from a starting-up mode to a printing mode, the fixing unit cannot generate the power control signal inside thereof, even when the problem is corrected and power to the fixing unit is restored. At such a time, the first control unit generates the power control signal so that the image forming apparatus will re-enter the same mode as before the power supply interruption.
The image forming apparatus may further comprise a cover-opening/closing detecting device which detects that a cover of the apparatus body is opened/closed,
wherein the switch device is turned off/turned on in response to the cover being opened/closed as detected by the cover-opening/closing detecting device.
Thereby, it is possible to completely stop supplying electricity to the fixing unit when the cover is opened. Thereby, it is possible to avoid a danger such as user receiving an electric shock.
When the cover is closed, a maximum level of power used by the fixing unit may be set and the switch device may be turned on.
Specifically, by first determining whether the power control signal is generated, and whether the level of power used by the fixing unit is set to the maximum level when the power control signal is not generated, but the level of power used by the fixing unit is set smaller than the maximum level when the power control signal is generated. Thereby, it is possible to restart heating of the fixing roller with a maximum level of power which is the same as that used before the cover is opened and closed.
Other objects and further features of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.